Manual transmissions for automobiles, trucks and the like commonly employ a shift lever located within the vehicle cab which is supported upon a spherical segment bearing for universal shift lever movement in two planes. The lower end of the shift lever is associated with an extension engaging the transmission gear operating fork or yoke. As the extension is normally rigidly associated with the shift lever vibrations occurring within the transmission due to the meshing of the gear teeth are transferred to the shift lever causing noise and distraction within the vehicle cab.
Such a transfer of the transmission vibrations to the shift lever has endeavored to be controlled by the use of vibration dampers or isolators located in the linkage system between the transmission gear shifting apparatus and the shift lever. In the past, arrangements have been employed wherein the lower end of the shift lever includes a spherical ball bearing member welded thereto, and the extension includes a separate tubular element welded to the lower end of the lever having an internal member having a lower end engaging the transmission gear operating yoke, and an upper end received within the extension bore. Vibration damping components, such as elastomeric rings, have been interposed between the stem and the extension to absorb vibrations, and while damping apparatus of this type has reduced the transfer of vibrations from the transmission to the shift lever the assembly of such components to the shift lever the welded two-part assembly has complicated the manufacture and installation of the shift lever with respect to the transmission, and added significant costs of manufacture.
It is an object of the invention to provide a transmission shift vibration damper capable of being directly mounted upon the lower end of a shift lever, and the damper includes a single homogeneous body into which the spherical bearing surface is incorporated for supporting the shift lever and the body includes a bore for receiving a yoke engaging stem and concise vibration damping elastomeric elements are imposed between the stem and the body to minimize the transmission of vibrations through the damper to the shift lever.
A further object of the invention is to provide a transmission shift vibration damper which is of a concise and readily manufacturable configuration and utilizes elastomeric rings capable of significant compression for damping the transfer of vibrations from a transmission to a shift lever.
A further object of the invention is to provide a transmission shift lever apparatus capable of absorbing the majority of vibrations transmitted thereto to prevent such vibrations from being imposed upon a shift lever, and wherein metal-to-metal contact between a gear shifting stem and the shift lever will occur under high shifting loads, and yet elastomeric elements effectively absorb vibrations under normal operating conditions.
In the practice of the invention a homogeneous and integral combination bearing-extension-vibration damper is attached to the lower end of a manually operated transmission shift lever. The damper body is of an elongated configuration having upper and lower ends, and a central bore longitudinally extends therethrough intersecting the ends.
The upper external end region of the damper body is in the form of a spherical segment ball, and a pin fixing the damper body to the shift lever permits the spherical bearing surface to support the shift lever in the transmission socket receiving the spherical bearing permitting the shift lever to be universally moved within two planes.
The lower region of the damper body extends into the vehicle transmission and the lower end receives the upper end of the gear shifting stem which is pivotally mounted within the body bore. While the lower end of the gear shifting stem is received within a groove or pocket of the transmission gear displacing yoke or hub, the upper end of the stem is pivotally connected within the body bore by a pivot pin, and as the diameter of that portion of the stem received within the body bore is less than the diameter of the body bore relative pivoting about the stem pivot pin between the stem and body is possible.
The stem end region within the body bore, both above and below the stem pivot, includes an axially extending recess receiving a pair of elastomeric rings whose outer periphery engages the body bore. Further, the stem end within the body bore includes a circular ridge of a diameter less than the body bore, and a similar ridge is located on the stem adjacent the lowermost end of the body. Thus, upon the occurrence of maximum deformation of the elastomeric rings due to a maximum pivoting occurring between the stem and damper body metal-to-metal contact between the ridges and the body bore will occur permitting high gear shafting forces to be transmitted to the transmission, if necessary.
A pair of elastomeric rings are received within each recess formed on the upper region of the stem to provide the degree of damping required, and to also give a desirable "feel" to the transmission shifting action. The axial dimension of the stem recesses is greater than the combined axial dimension of the elastomeric rings received therein wherein deformation of the rings can be accommodated without overstressing of the elastomeric material.
The unitary construction of the vibration damper body and the utilization of improved vibration damping elements, in accord with the invention, has produced an advance over the art with respect to previous developments of this type. The invention eliminates welding operations during assembly and manufacturing costs are substantially reduced.